Ultrasound





Ultrasound directed to the brain can boost human sensory performance

 

US-based Virginia Tech Carilion Research Institute scientists have demonstrated that ultrasound directed to a specific region of the brain can boost performance in sensory discrimination.

Whales, bats, and even praying mantises use ultrasound as a sensory guidance system – and now a new study has found that ultrasound can modulate brain activity to heighten sensory perception in humans.

The study, published online January 12, 2014 in Nature Neuroscience, provides the first demonstration that low-intensity, transcranial- focused ultrasound can modulate human brain activity to enhance perception.

“Ultrasound has great potential for bringing unprecedented resolution to the growing trend of mapping the human brain’s connectivity,” said William “Jamie” Tyler, an assistant professor at the Virginia Tech Carilion Research Institute, who led the study. “So we decided to look at the effects of ultrasound on the region of the brain responsible for processing tactile sensory inputs.”

The scientists delivered focused ultrasound to an area of the cerebral cortex that corresponds to processing sensory information received from the hand. To stimulate the median nerve – a major nerve that runs down the arm and the only one that passes through the carpal tunnel – they placed a small electrode on the wrist of human volunteers and recorded their brain responses using electroencephalography, or EEG. Then, just before stimulating the nerve, they began delivering ultrasound to the targeted brain region.

The scientists found that the ultrasound both decreased the EEG signal and weakened the brain waves responsible for encoding tactile stimulation.

The scientists then administered two classic neurological tests: the two-point discrimination test, which measures a subject’s ability to distinguish whether two nearby objects touching the skin are truly two distinct points, rather than one; and the frequency discrimination task, a test that measures sensitivity to the frequency of a chain of air puffs.

What the scientists found was unexpected.

The subjects receiving ultrasound showed significant improvements in their ability to distinguish pins at closer distances and to discriminate small frequency differences between successive air puffs. “Our observations surprised us,” said Tyler. “Even though the brain waves associated with the tactile stimulation had weakened, people actually got better at detecting differences in sensations.”

Why would suppression of brain responses to sensory stimulation heighten perception? Tyler speculates that the ultrasound affected an important neurological balance.

“It seems paradoxical, but we suspect that the particular ultrasound waveform we used in the study alters the balance of synaptic inhibition and excitation between neighbouring neurons within the cerebral cortex,” Tyler said. “We believe focused ultrasound changed the balance of ongoing excitation and inhibition processing sensory stimuli in the brain region targeted and that this shift prevented the spatial spread of excitation in response to stimuli resulting in a functional improvement in perception.”

To understand how well they could pinpoint the effect, the research team moved the acoustic beam one centimetre in either direction of the original site of brain stimulation – and the effect disappeared. “That means we can use ultrasound to target an area of the brain as small as the size of an M&M,” Tyler said. “This finding represents a new way of noninvasively modulating human brain activity with a better spatial resolution than anything currently available.”

Based on the findings of the current study and an earlier one, the researchers concluded that ultrasound has a greater spatial resolution than two other leading noninvasive brain stimulation technologies – transcranial magnetic stimulation, which uses magnets to activate the brain, and transcranial direct current stimulation, which uses weak electrical currents delivered directly to the brain through electrodes placed on the head.

“Gaining a better understanding of how pulsed ultrasound affects the balance of synaptic inhibition and excitation in targeted brain regions – as well as how it influences the activity of local circuits versus long-range connections – will help us make more precise maps of the richly interconnected synaptic circuits in the human brain,” said Wynn Legon, the study’s first author and a postdoctoral scholar at the Virginia Tech Carilion Research Institute.

“We hope to continue to extend the capabilities of ultrasound for noninvasively tweaking brain circuits to help us understand how the human brain works.” “The work by Jamie Tyler and his colleagues is at the forefront of the coming tsunami of developing new safe, yet effective, noninvasive ways to modulate the flow of information in cellular circuits within the living human brain,” said Michael Friedlander, executive director of the Virginia Tech Carilion Research Institute and a neuroscientist who specializes in brain plasticity.

“This approach is providing the technology and proof of principle for precise activation of neural circuits for a range of important uses, including potential treatments for neurodegenerative disorders, psychiatric diseases, and behavioural disorders. Moreover, it arms the neuroscientific community with a powerful new tool to explore the function of the healthy human brain, helping us understand cognition, decision-making, and thought.

This is just the type of breakthrough called for in President Obama’s BRAIN Initiative to enable dramatic new approaches for exploring the functional circuitry of the living human brain and for treating Alzheimer’s disease and other disorders.”

A team of Virginia Tech Carilion Research Institute scientists – including Tomokazu Sato, Alexander Opitz, Aaron Barbour, and Amanda Williams, along with Virginia Tech graduate student Jerel Mueller of Raleigh, N.C. – joined Tyler and Legon in conducting the research. In addition to his position at the institute, Tyler is an assistant professor of biomedical engineering and sciences at the Virginia Tech-Wake Forest University School of Biomedical Engineering and Sciences. In 2012, he shared a Technological Innovation Award from the McKnight Endowment for Neuroscience to work on developing ultrasound as a noninvasive tool for modulating brain activity.

“In neuroscience, it’s easy to disrupt things,” said Tyler. “We can distract you, make you feel numb, trick you with optical illusions. It’s easy to make things worse, but it’s hard to make them better. These findings make us believe we’re on the right path.”

doi:10.1038/nn.3620
 

Breast cancer – combining imaging techniques for quicker and gentler biopsies

Taking tissue samples can often be a traumatic experience for breast cancer patients. There are also significant costs associated with the procedure when magnetic resonance imaging is used. Fraunhofer scientists working on the MARIUS project are developing a more cost-effective biopsy method that is easier on patients. They showcased new alternative technologies and techniques combining MR and ultrasound imaging at MEDICA 2013 in Düsseldorf, Germany in November.

How can you tell if a breast tumour is malignant? This isn’t a question that ultrasound and X-rays, or even magnetic resonance scans, can answer alone. Doctors must often extract tissue samples from an affected area with a fine needle for detailed examination. This sort of biopsy is often undertaken with the help of ultrasound, with doctors observing a screen for needle guidance. Unfortunately, around 30% of all tumours are invisible to ultrasound.

In some cases, magnetic resonance imaging (MRI) is used to ensure correct needle insertion. This process involves two steps: the imaging itself, which takes place inside the MRI scanner, and the insertion of the biopsy needle, for which the patient must be removed from the machine to insert the needle accurately. This process is often repeated several times before the sample is finally taken. This exhausts patients and is also costly, because the procedure occupies the MRI scanner for a significant period.

In the joint MARIUS project (Magnetic Resonance Imaging Using Ultrasound – systems and processes for multimodal MR imaging), experts from both the Fraunhofer Institute for Biomedical Engineering IBMT in St. Ingbert and the Fraunhofer Institute for Medical Image Computing MEVIS in Bremen are working together towards a quicker and gentler alternative.

Combining imaging techniques intelligently

The new technique would require just one scan of the patient’s entire chest at the beginning of the procedure, meaning that the patient only has to enter the scanner once. The subsequent biopsy is guided by ultrasound; the system would transform the initial MRI scan and accurately render it on screen. Doctors would have both the live ultrasound scan and a corresponding MR image available to guide the biopsy needle and display exactly where the tumour is located.

The biggest challenge is that the MRI is performed with the patient lying prone, while during the biopsy she lies on her back. This change of position alters the shape of the patient’s breast and shifts the position of the tumour significantly. To track these changes accurately, researchers have applied a clever trick: While the patient is in the MRI chamber during the scan, ultrasound probes, which resemble ECG electrodes, are attached to the patient’s skin to provide a succession of ultrasound images. This produces two comparable sets of data from two separate imaging techniques.

When the patient undergoes a biopsy in another examination room, the ultrasound probes remain attached and continually record volume data and track the changes to the shape of the breast. Special algorithms analyze these changes and update the MRI scan accordingly. The MR image changes analogously to the ultrasound scan. When the the biopsy needle is inserted into the breast tissue, the doctor can see the reconciled MRI scan along with the ultrasound image on the screen, greatly improving the accuracy of needle guidance towards the tumour.

Ultrasound equipment suitable for use in an MRI Scanner

To realize this vision, Fraunhofer researchers are developing a range of new components. “We’re currently working on an ultrasound device that can be used within an MRI scanner,” says IBMT project manager Steffen Tretbar. “These scanners generate strong magnetic fields, and the ultrasound device must work reliably without affecting the MRI scan.” Ultrasound probes that can be attached to the body to provide 3D ultrasound imaging are also being developed by the team as part of the project.

The software developed for the technique is also completely new. “We’re developing a way to track movements in real time by means of ultrasound tracking,” explains MEVIS project manager Matthias Günther. “This recognizes distended structures in the ultrasound images and tracks their movement. We also need to collate a wide range of sensor data in real time.” Some of the sensors gather data about the position and orientation of the attached ultrasound probes while others track the position of the patient.

The team showcased the entire concept and an initial demonstrator of the technology in November at the MEDICA 2013 trade fair in Düsseldorf. The next version is set to be completed next year. Whereas the IBMT team is developing the hardware and new ultrasound techniques, the MEVIS working group is concentrating on the software.

The primary objective of MARIUS is to develop ultrasound tracking to aid breast biopsies. Nevertheless, the developed components could also be used in other applications. For instance, the MARIUS system and its movement-tracking software could allow slow imaging techniques such as MRI or positron emission tomography (PET) to accurately track the movements of organs that shift even when a patient is lying still. Aside from the liver and the kidneys, which change shape and position during breathing, this includes the heart, whose contractions also cause motion. Thanks to a technique applied to reconstruct the image, the heart would appear well defined on MRI scans instead of blurred. The jointly developed technology could also be applied to treatments that use particle or X-ray beams. For tumors located in or on a moving organ, the new technology could target the rays so that they follow the movement.These beams could hit the tumor with more precision than currently possible and reduce damage to healthy surrounding tissue.

Recent acquisitions in diagnostic ultrasound market light way for positive year ahead – analyst

Major deals concluded within the diagnostic ultrasound imaging market throughout 2013 translate into “a year to look forward to” in 2014, as innovation is fuelled by heightened demand in what has previously been considered a technologically conservative market, says an analyst with research and consulting firm GlobalData.

According to Niharika Midha, GlobalData’s Analyst covering Diagnostic Imaging, a pattern has emerged across the various deals being undertaken in the diagnostic ultrasound market. The majority of acquisitions made in 2013 have resulted in diversified product portfolios, allowing companies to strengthen their high- and low-end offerings.

Midha says: “A good example of this is Analogic Corporation’s acquisition of Canadian-based Ultrasonix, which resulted in the expansion of Analogic’s ultrasound product portfolio from the offering of its existing ultrasound imaging subsidiary, BK Medical.

Analogic paid $83 million in cash for Ultrasonix, underscoring the former company’s efforts to increase its market presence by introducing systems that can be purchased at different price points.” Analogic went on to acquire a majority stake in PocketSonics in October 2013, further enhancing its pipeline on the point-of-care ultrasound front.

Global- Data expects strong growth for Analogic’s ultrasound business segment in the coming fiscal year, as point-of-care technology and price-sensitive economies are estimated to offer maximum potential for expansion. Indeed, the company’s ultrasound business generated 27% of its fiscal year revenue in 2013.

Another major deal was the acquisition of Zonare Medical Systems by Chinese ultrasound manufacturer Mindray, for $102 million. This has allowed Mindray to capture a share in the high-end ultrasound market and will ultimately enable it to gain additional share in all developed nations where it currently lags behind other market players.

The year ended with Konica Minolta acquiring the ultrasound business segment of Panasonic Healthcare. Konica Minolta, which is keen on venturing into this space, launched a handheld system in December 2013, while adding products from Panasonic Healthcare’s portfolio, effective in January 2014.

Midha continues: “We’re expecting similar deals to continue taking place throughout 2014, as giant firms look to expand their product portfolios by swallowing up smaller companies that have developed novel technologies with proven superiority to existing products.

“Diagnostic ultrasound is currently the most widely used and steadily growing imaging technique across the globe, and acquisitions provide an opportunity both for established companies to increase their presence in the market and for new players to gain entry,” the analyst concludes.



Study on MRI-ultrasound for targeted prostate biopsy shows improved sensitivity

Using Magnetic Resonance Imaging- Ultrasound (MRIUS)- guided prostate biopsy has high sensitivity to detect prostate abnormalities compared with transrectal ultrasonography (TRUS biopsy) of MRI positive findings.

The study won the first prize from Karl Storz for best poster at the EAU 13th Central European Meeting (CEM) held in October last year in Prague, Czech Republic.

“The systematic 12-core transrectal ultrasound guided biopsy (TRUS biopsy) which is currently considered the standard of care for the diagnosis of prostate cancer (PCa), misses many small, non-palpable and ultrasound invisible lesions,” said presenting author Anna Katarzyna Czech of the Dept. of Urology, Jagiellonian University in Krakow, Poland.

Although the new imaging modalities, including MRI, have improved the rate of tissue abnormality detection, Czech said these procedures are time consuming and uncomfortable for a patient which limits their use.

“However, by fusing MRI with TRUS images it became possible for the urologist to perform the MRI guided TRUS biopsies in the office setting,” she added. In their study, Czech and colleagues used the real-time fusion of TRUS images with previously recorded MR images (MRIUS), based on linear interpolation of pixels.

Eighty men, who had prostate lesions detected exclusively in the transrectal prostate magnetic resonance imaging, were included in the study. All men were randomised into two groups (40 patients each) and underwent TRUS guided biopsy.

In group I, TRUS biopsies of MRI identified lesions were performed, while in group II: biopsies of the lesions visualised in MRI were performed using MRIUS method which allowed for the real-time fusion of TRUS images with previously recorded MR images.

Histopathological examination of TRUS guided prostate biopsy of MRI identified lesions was positive for prostate cancer in 8 cases, for ASAP and HGPIN in 3 and for chronic prostatitis in 5. No microscopic pathologies were identified in 24 patients.

In group II, there were 17 cases of prostate cancer, 8 of ASAP and HGPIN, and 8 of chronic prostatitis found. In 8 out of 40 men, histopathological examination identified no abnormalities.

In their results, the researchers said MRIUS guided prostate biopsy yielded 22.5%, 10% and 7.5% more prostate cancer, ASAP and HGPIN and chronic prostatitis cases, respectively compared with TRUS biopsies of the MRI identified lesions. The sensitivity to identify microscopically confirmed prostate abnormalities was 40% (95% CI: 24.9-56.7) with TRUS guided prostate biopsy of MRI identified lesions and 80% (95% CI: 64.4-90.9) with MRIUS method. This difference was statistically significant (p=0.001). “Fusion technology guided biopsy yielded 42.5% more prostate abnormalities than the TRUS biopsy of MRI positive lesions.

Moreover, MRIUS targeted biopsies were sufficient in all PCa cases to determine their clinical significance, making the fusion technology a potential solution for the patients with clinical suspicion of prostate cancer,” explained Czech.

She added that further research will determine the relevance of an endorectal coil used during MRI for prostate deformation, and gland volume measurements, as well as the feasibility of MRIUS in order to detect PCa in larger prostates.

She also noted that the use of 3Tesla MRI for fusion technology, which would eliminate use of endorectal coil, needs to be investigated. Despite these limitations the authors pointed out that MRIUS guided prostate biopsy has high sensitivity to detect prostate abnormalities. “It markedly improved ability to detect clinically significant lesions compared with TRUS biopsy of MRI positive findings,” they said.

 Date of upload: 09th Apr 2014

 

                                  
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